The present invention relates to a method of and an apparatus for the production of mold parts for foundries using a pressure vessel arranged to be filled with a granular composition, and to supply the composition into a molding device.
Mold producing apparatuses are well-known in the art, German Pat. No. 620,779 shows a sand blowing machine where material can be blown from a fixed storage vessel via a fixed intermediate vessel into a core box. By opening two valves, the intermediate vessel is filled with the material and then, by closing the valves and opening two additional valves, the contents of the intermediate vessel are discharged into the core box, whereupon the additional two valves are again closed. When the storage vessel is evacuated, the cover can be removed and the vessel refilled.
Swiss Pat. No. 183,838 discloses a method of evacuating storage vessels containing granular material using a gaseous pressure medium acting on the surface of the material charged in the vessel, and a movable plate contained in the vessel. To fill the storage vessel, the cover of the vessel is removed along with the parts connected to it and after refilling, the cover is replaced. A special airlock can be placed on the storage vessel for use during the filling operation. In an intermediate phase of the operation, the granular material can be transferred into opened airlocks after which they are closed.
German Pat. No. 1,162,033 shows a shot machine for making foundry molds and cores which correlates a compressed air storage chamber with a vessel for receiving granular composition and surrounded by an interspace. The storage chamber, filled with compressed air, is connected by means of a quick-action shot valve with a large passage opening to the filled, closed sand vessel. The granular composition flows via several nozzles into a mold box, or the like, and fills it. After the filling, the shot machine is vented via a membrane valve. A refill vessel arranged above the sand vessel and firmly connected to it, is spatially separated from it by a closed slide valve. By opening the slide valve, the vessel is filled with the granular composition, whereupon the slide valve is closed.
The above devices, however, have the disadvantages that they must blow the granular composition either by means of compressed air from a storage vessel into an intermediate vessel and then into a core box, or that, because of the time consuming manner of filling the storage vessel, they must select a very large volume or use additional compressed air storage chambers, and, therefore, operate with very high compressed air consumption.
Further disadvantages lie in that the storage vessels connected with the pressure vessels for receiving the granular composition can, for structural reasons, contain only small volumes, and, therefore, lead to frequent stoppages for refilling.
Another disadvantage is that the storage and pressure vessels are fixedly connected together. Thus, it is necessary to lift the core boxes which are to be filled before the filling process, and to lower them again after finishing the process. This limits the application of the blowing method.
The development of organic binders for granular compositions widened the area of application of the shooting of foundry mold parts. As a result, the amount of granular composition required per hour is increased. Therefore, a definite disadvantage ensues because the large volume storage bins could not be directly correlated to the devices developed for the blowing method.